Antimicrobial active ingredients have been used in a wide variety of applications. Recently, there has been an increased interest in encapsulating active ingredients for various reasons, including managing active ingredient release from compositions. On particular active ingredient of interest are metal pyrithiones.
Metal pyrithione compounds, such as zinc pyrithione, have been used as an active ingredient in a wide variety of uses, including as anti-dandruff agents, and as anti-fungal, anti-mildew and/or anti-microbial additives to plastics, paints and coatings. However, adding zinc pyrithione to plastics, in particular chlorine containing plastics, such as polyvinylchloride (PVC), results in the problem of yellowing of the plastic. This is especially true for those formulations which are calendared or extruded at high temperatures and/or high shear. This yellowing problem also exists in plastics containing chlorides when the plastic is exposed to light.
Not wishing to be bound by theory, it is believed that high temperature, high shear and/or light may cause hydrochloric acid (HCl) to be formed in the polymer matrix. When HCl is formed, the zinc in the zinc pyrithione may react with hydrochloric acid formed in the PVC, thereby forming zinc chloride. Zinc chloride in the polymer matrix, in turn, tends to catalyze the degradation of the polyvinylchloride, thereby causing the yellowing.
In order to stabilize chlorine containing polymers against degradation when a pyrithione containing compound is added to provide mildew resistance, fungal resistance and antimicrobial properties, it has become necessary to add a scavenger for HCl into the polymer matrix. As such, adding additional ingredients may make it more difficult to process the chloride containing polymer, as well as to add cost to the final product.
Accordingly, there is a need in the art for a pyrithione additive for chlorine containing polymers which does not require the addition of further ingredients to stabilize the chloride containing polymer from degradation.
In addition, there is a need in the art for stabilized or encapsulated active ingredients in other uses, including but not limited to, providing antimicrobial properties to other polymers, such as polyurethanes, in architectural coating, in antifouling paints, in personal care products, such as shampoos and the like.